AOPA has told the FAA that December 2004 is too early to implement domestic reduced vertical separation minima (DRVSM). In comments on the proposed DRVSM rule, AOPA said neither the FAA nor the industry could recertify the thousands of turbine-powered general aviation aircraft that will have to be modified in time to meet the deadline. And while DRVSM is supposed to increase capacity at altitude, AOPA pointed out that the major chokepoints remain the terminal areas. Until more runways are built, DSRVM will have little impact on improving total system capacity.

DRVSM will implement a 1,000-foot vertical separation standard between FL290 and FL410 (29,000 to 41,000 feet msl) Currently, the vertical separation minimum at these altitudes is 2,000 feet due to limitations in aircraft instrumentation and altitude-keeping capabilities.

Once DRVSM is implemented, turbine operators will have to upgrade their altimeters, autopilots, and other equipment and recertify the aircraft to the new standards. Not only is that expensive (as much as $250,000 for older generation aircraft), it is also time consuming. Aircraft that aren't certified for RVSM will be prohibited from flying above FL290.

"Because our fleet is far less homogenous than that of the airlines, the time needed to develop service bulletins and make the necessary airframe and avionics modifications is much greater than the proposed time period," said Melissa Bailey, AOPA's vice president of air traffic and regulatory and certification policy. "The only responsible course of action is follow an incremental implementation strategy and phase in DRVSM at higher altitudes first."

AOPA favors a phasing in of DRVSM at FL350 to FL390 by December 2004, followed by implementation at the lower altitudes by December 2006.